Regular readers will be well aware of my obsession with bioluminescence, that beautiful light produced by things like fireflies and glow worms. So I was excited to see this paper in the Proceedings of the National Academy of Sciences.
Margarita Zarubin and colleagues have discovered why so many non-symbiotic marine bacteria are bioluminescent. It turns out that the light gets the bacteria to where they ultimately want to be, inside the digestive tract of fish. While it may not appeal to you or me, fish guts are some bugs idea of bacterial nirvana – all the food you can eat, a safe haven from predators and a convenient means of transport.
Here’s how it seems to work. Using the bioluminescent marine bacterium, Photobacterium leiognathi, Zarubin and colleagues found that zooplankton, attracted by the light, ingest the bacteria but are then unable to digest them. Unfortunately for the zooplankton, the bacteria continue to glow, revealing the presence of the hapless zooplankton to their own predators, nocturnal fish, who were now able to easily spot the glowing zooplankton in the dark water, and devour them. Zarubin and colleagues also showed that fish weren’t attracted to zooplankton who had ingested mutated P. leiognathi that no longer glowed. P. leiognathi were also found to survive the transit through the fish digestive system. Hey presto, they’ve reached nirvana! How neat is that? Survival of the brightest indeed.
Reference: M. Zarubin, S. Belkin, M. Ionescu, A. Genin (2011). Bacterial bioluminescence as a lure for marine zooplankton and fish. Proceedings of the National Academy of Sciences 109 (3): 853 DOI: 10.1073/pnas.1116683109.